Don't expect much of an audience for this on Lemmy, but:

Maybe it's just the places I've worked, but seems like I'm constantly wading through contacts who are gone - I don't want to delete them because the history could be helpful, but seems like there should be a quick, native way to mark them. Maybe once marked those names are grayed out or something.

My one company had a custom field that you could check, but then there was no special handling of those contacts in terms of how they're displayed - just you could use it to exclude results in reports.